Flickr/Charlotte.MorrallWe're always on the lookout for ways to transform our lives, but sometimes we forget that — along with exercise— another miracle drug for our brains and bodies is within reach: sleep.

If you have a few days off this summer, one of the best things you can do with your time is fix your sleeping habits. Just let yourself sleep naturally during those days and see how much you really need.

1. You'll be happier.

Sleeping poorly ruins your day. You know that, but researchers have shown it too, especially in one notable study that followed 909 working women. A poor night's rest affected their happiness as much as tight work deadlines, and it had an even bigger impact on mood than significant income differences in the group.

4. You'll learn better.

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This isn't just about kids. Adults who get enough sleep do better on tests of short-term memory.

And when researchers had adults do a task once, get a good night's sleep, and then try the task again, they showed improvement. But participants who stayed awake 30 hours after learning the same task had a much harder time improving their skills - even if they practiced and had a chance to catch some recovery shut eye later. Something about the initial sleep deprivation impaired their ability to learn.

Of course, letting kids get enough sleep is important too. In one case, starting schools an hour later (at 8:30 instead of 7:30) increased"standardized test scores by at least 2 percentile points in math and 1 percentile point in reading." The Minneapolis school district found that starting school an hour and a half later (7:15 to 8:40) improved attendance and led to fewer symptoms of depression among students.

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5. It's one of the best ways to stay fit.

Multiple studies show that people who sleep less are more likely to be obese. One study that followed 500 people for 13 years found that people who regularly slept less than seven hours a night were 7.5 times more likely to be overweight - even after controlling for physical activity, family history, and demographic factors.

Researchers think this is mostly due to hormonal changes caused by sleep deprivation - not getting enough sleep stimulates your appetite. Basically, one of the most effective diet hacks possible is just getting enough sleep.

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6. People who don't sleep enough are more likely to develop diabetes — even if they are skinny.

Type 2 diabetes is an awful disease that can lead to strokes, amputations, blindness, and organ damage. And this isn't just about obesity, so if you are skinny but don't get enough sleep this still applies.

Otherwise healthy adults lose their ability to control blood sugar without getting enough sleep, and the less sleep someone gets, the more likely they are to develop a problem. Compared to adults who sleep seven to eight hours a night, people who sleep six hours are 1.7 times as likely to develop diabetes, and people who sleep five hours are 2.5 times as likely to develop diabetes.

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7. People who sleep enough have better moods and fewer problems with depression and anxiety.

People who sleep less tend to have more symptoms of depression, lower self esteem, and more anxiety - though that's an association and it's possible that those symptoms cause people to sleep less.

Still, a review of studies shows that sleep loss has an even stronger effect on mood than it does on cognitive ability or motor function, which is a strong indicator that sleeping more could help.

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8. People who get more sleep have healthier skin.

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Along with mood disorders, sleeping poorly is also associated with chronic skin conditions. Some research shows that poor sleep, depression, anxiety, and chronic skin problems all go together.

A study published in Clinical and Experimental Dermatology found that "good sleepers" recovered better after ultraviolet light exposure, and their skin also recovered more quickly after having tape stripped off of it. They also showed fewer signs of aging.

9. Adolescents who sleep enough are less likely to abuse alcohol.

Adolescents who have sleeping problems are more likely to develop problems abusing alcohol - though it's also true that people who abuse alcohol have trouble sleeping well.

Still, researchers believe that having a disrupted circadian rhythm causes changes in the reward system of the brain. This, in turn, makes those adolescents more likely to engage in risky behavior and to develop alcohol use disorders.

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10. It'll be easier to speak well.

We know that people who drive tired are similar to those who drive drunk, but did you know that staying awake too long can cause slurred speech, repetitive word usage, and a slow, monotonous tone? So make sure to get some rest before your next presentation.

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11. Getting enough sleep helps prevent migraines and other headaches.

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If you find yourself cringing due to sudden head pain, look at your sleep schedule. Even though doctors aren't sure exactly why this happens, multiple studies show that people who don't sleep enough are more likely to suffer migraines. "Poor sleep quality is uniquely associated with episodic migraine," write the authors of one recent study (emphasis ours).

Additionally, 36 to 58% of sleep apnea sufferers wake up with a throbbing head.

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12. You'll be more productive at work and more focused at home.

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The more tired you are, the harder it to concentrate on something, and distraction can take a toll on both work and your personal life.Researchers say that "attention tasks appear to be particularly sensitive to sleep loss." So if you want to focus - either on a job or a conversation - make sure to get some rest.

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13. You'll make fewer dangerous mistakes.

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Though we don't always recognize it, we make more mistakes when we don't get enough sleep. For some of us that amounts to a typo here and there, which is annoying to our editors, but such carelessness can be more serious.

In 2003, the body that regulates medical residents' hours decided to limit those hours to 80 hours a week with no shifts longer than 24 hours (there's a reason why medical residents show up frequently in sleep deprivation studies). But a Harvard study afterwards found that if those hours were further reduced to 63 a week, residents slept more and made fewer serious medical errors. The more sleep-deprived group made 22% more serious errors.

Famous accidents like the Space Shuttle Challenger explosion and the Exxon Valdez oil spill have been attributed, at least in part, to mistakes made by people who didn't get enough sleep. But it's not just these major events: All sleep-deprived workers are much more likely to have a dangerous accident.

One study of 50,000 people in Sweden found that lack of sleep made people twice as likely to die in an accident.

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14. You'll see better if you get enough sleep.

We don't function well without sleep. Our bodies get tired and our eyes get tired. The longer you stay awake, the more vision errors you make, ranging from tunnel vision to seeing double to even - eventually, at scary levels of sleep loss - hallucinations.

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15. You'll be less likely to catch a cold.

While going out in the cold doesn't make you more likely to catch one, being exposed to one does. But if you haven't slept before being exposed to a virus, your weakened immune system makes you much more likely to catch it. When researchers exposed a group of 153 people to the common cold, those who had been sleeping less than seven hours a night were almost three times more likely to catch the virus.

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16. You're less likely to develop certain kinds of cancer.

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People who do shift work (night shifts) and have disrupted circadian cycles - and thus don't sleep enough - are likely to encounter some serious health problems. One association that researchers have found is that these night workers are more likely to develop colon and breast cancer.

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17. You'll be less easily irritated or upset.

When you don't sleep enough you're more emotionally volatile and more easily irritated - a little thing can make you blow up or ruin your morning even more. According to a study published by an Israeli research team, sleep deprivation amplifies negative emotions caused by small things like interruptions. The researchers studied medical residents, who as we know are tragically familiar with not getting enough sleep.

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18. People feel less pain after a good night of sleep.

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Not getting enough sleep makes people more sensitive to pain - which can lead to a terrible cycle for chronic pain sufferers. Tests show that keeping people up all night makes it easier for them to feel pain. There's even evidence that not getting enough sleep can interfere with the pain relief processes of certain drugs. By the same token, getting good sleep can function like low level pain medication.

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19. You'll have quicker reflexes.

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Researchers have tested college athletes and West Point cadets - pretty fit groups with pretty well-honed reactions in the first place. Overall strength isn't necessarily affected by losing a night's sleep, but after one sleep-deprived night people's reactions aren't as quick. The researchers theorize this is probably caused by a diminished ability to use information to make decisions.

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20. People who sleep enough have fewer heart problems.

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One large study found that sleeping five hours or less a night was associated with a 45% increased risk for heart attacks. Keeping people awake increases their blood pressure - even healthy young men who have one bad night of only 3.6 hours of sleep show significant temporary changes.

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...And beyond these positive health effects, you'll spend less time and money at the doctor.

People who score high on a "sleepiness scale" use 11% more healthcare resources than their well-rested brethren. Sleep troubles caused by sleep apnea and insomnia cost the US billions of dollars in direct medical costs every year, and that's even before taking into account the associated lost productivity.

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You'll be a better and safer driver.

You'll definitely want to be well-rested if you are going to take a flying car out for a spin.
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Drowsy driving is responsible for 100,000 crashes and 1,500 deaths every year, according to the National Sleep Foundation. Almost 20% of serious injuries in crashes happen when there's a sleepy driver involved.

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And you'll be less likely to make risky financial decisions.

When people are tired, the way they make financial decisions changes. Instead of trying to minimize loss, they start looking for risky big gains. That's a good reason to make sure you sleep before making any big purchases - and it also raises some questions about the insane hours some Wall Street employees log.